RETARDER GP-ELECTRIC 5400969 - Caterpillar

CID 0041 FMI 03 service code is recorded when the ECM reads the voltage of the 8 volt DC supply circuit (wire R800-OR(Orange)) as higher than the normal voltage. The following causes could signal this diagnostic code:
The 8 volt DC supply circuit (wire R800-OR(Orange)) is shorted to the +battery circuit.
The ECM has failed. This is unlikely.Note: Ensure that the CID 0041 - FMI 03 is active.Note: Use a digital multimeter for the measurements in this procedure.System Response:Components that receive power from the 8 volt DC supply will not be available.Test Step 1. CHECK THE HARNESS FOR A SHORT TO THE +BATTERY CIRCUIT.
The disconnect switch and the key start switch remain in the ON position.
Without disconnecting the harness, disconnect pin J1-44 from the ECM.
At the harness side of the connector for the ECM, measure the voltage from connector contact J1-44 (8 volt DC supply) to frame ground. Expected Result:The voltage is 0.0 0.5 DCV.Results:
OK - The voltage is 0.0 0.5 DCV. The voltage is correct. Proceed to Test Step 2.
NOT OK - Voltage is NOT 0.0 0.5 DCV. The harness has failed.Repair: The machine harness is shorted to the +battery circuit. Repair the machine harness or replace the machine harness.STOPTest Step 2. CHECK FOR THE CORRECT VOLTAGE AT THE ECM.
Turn the disconnect switch and the key start switch to the ON position.
Check the voltage at the connector of the ECM from contact J1-44 (8 volt DC supply) to contact J1-45 (ground). Use the multimeter probes to measure the voltage. Do NOT disconnect the machine harness from the ECM. Wiggle the connector in order to make sure that there is a strong connection. Expected Result:The voltage is 8.0 0.5 DCV.Results:
OK - Voltage is 8.0 0.5 DCV. The 8 volt DC supply voltage is correct. Verify that the diagnostic code is present. If the diagnostic code is still present, the ECM may have failed. Replace the ECM.STOP
NOT OK - Voltage is greater than 8.0 0.5 DCV. The 8 volt DC supply voltage is NOT correct. The ECM has failed.Repair: Check the circuit again. If the Caterpillar Electronic Technician (Cat ET) is available, use the Cat ET service tool in order to perform a “Wiggle Test” on the machine wiring harness. The “Wiggle Test” can detect shorts and opens in the machine wiring harness that are momentary or intermittent.It is unlikely that the ECM has failed. Exit this procedure and perform this procedure again. If the cause of the diagnostic code is not found, replace the ECM. See Testing and Adjusting, "Electronic Control Module (ECM) - Replace". STOP